Special Issue Information

Dear Colleagues,

Air quality and climate change issues are at the forefront of our national environmental agenda. Vast differences exist between geographic areas regarding local pollutant emissions, air pollution formation, transport of pollutants, and climate. The Intergovernmental Panel on Climate Change (IPCC) projected “declining air quality in cities” into the future in response to climate change based on future climate scenarios and no emission reductions.

Air quality and climate are intricately connected through complex interactions. For instance, ozone and particle formation are highly dependent on weather and would hence respond to climate change, while changes in ozone and particles can in turn impact climate, as the former is a greenhouse gas and the latter affects energy budget via its optical properties. Moreover, any increases or decreases in ozone and particle concentrations are linked to changes in concentrations of their precursors through numerous chemical and physical processes. In general, atmospheric chemistry-climate interactions are still poorly understood.

Manuscripts on all aspects of air quality and climate are welcome for this special issue.

Dr. Huiting MaoGuest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Atmosphere is an international peer-reviewed Open Access monthly journal published by MDPI.

Abstract: Due to the highly heterogeneous and dynamic nature of urban areas in Chinese cities, air pollution exhibits well-defined spatial variations. Rapid urbanization in China has heightened the importance of understanding and characterizing atmospheric particulate matter (PM) concentrations and their spatiotemporal variations. To investigate the small-scale spatial variations in PM in Xiamen, total suspended particulate (TSP), PM10, PM5 and PM2.5 measurements were collected between August and September in 2012. Their average mass concentrations were 102.50 μg∙m−3, 82.79 μg∙m−3, 55.67 μg∙m−3 and 43.70 μg∙m−3, respectively. Organic carbon (OC) and elemental carbon (EC) in PM2.5 were measured using thermal optical transmission. Based on the PM concentrations for all size categories, the following order for the different functional areas studied was identified: hospital > park > commercial area > residential area > industrial area. OC contributed approximately 5%–23% to the PM2.5 mass, whereas EC accounted for 0.8%–6.95%. Secondary organic carbon constituted most of the carbonaceous particles found in the park, commercial, industrial and residential areas, with the exception of hospitals. The high PM and EC concentrations in hospitals were primarily caused by vehicle emissions. Thus, the results suggest that long-term plans should be to limit the number of vehicles entering hospital campuses, construct large-capacity underground parking structures, and choose hospital locations far from major roads.

Abstract: Suspended particles with aerodynamic diameters not greater than 1 μm (PM1) were sampled at the urban background; regional background; and urban traffic points in southern Poland. In total, 120 samples were collected between 2 August 2009 and 27 December 2010. Sixteen polycyclic aromatic hydrocarbons (PAHs) were determined in each sample. The samples were collected with a high volume sampler (Digitel). Afterwards, they were chemically analyzed with a gas chromatograph equipped with a flame ionization detector (Perkin Elmer Clarus 500). The mean concentration values of the PAH sum (ΣPAH) and particular PAHs; the percentages of carcinogenic PAHs in total PAHs (ΣPAHcarc/ΣPAH); carcinogenic equivalent (CEQ); mutagenic equivalent (MEQ); and TCDD-toxic equivalent (TEQ) were much higher in the winter (heating) season than in the summer (non-heating) one. For both periods, the resulting average values obtained were significantly higher (a few; and sometimes a several dozen times higher) in the researched Polish region than the values observed in other areas of the world. Such results indicate the importance of health hazards resulting from PM1 and PM1-bound PAHs in this Polish area.

Abstract: An analysis of coastal meteorological mechanisms facilitating the transit pollution plumes emitted from sources in the Northeastern U.S. was based on observations from the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) 2004 field campaign. Particular attention was given to the relation of these plumes to coastal transport patterns in lower tropospheric layers throughout the Gulf of Maine (GOM), and their contribution to large-scale pollution outflow from the North American continent. Using measurements obtained during a series of flights of the National Oceanic & Atmospheric Administration (NOAA) WP-3D and the National Aeronautics and Space Administration (NASA) DC-8, a unique quasi-Lagrangian case study was conducted for a freshly emitted plume emanating from the New York City source region in late July 2004. The development of this plume stemmed from the accumulation of boundary layer pollutants within a coastal residual layer, where weak synoptic conditions allowed for its advection into the marine troposphere and transport by a mean southwesterly flow. Upon entering the GOM, analysis showed that the plume layer vertical structure evolved into an internal boundary layer form, with signatures of steep vertical gradients in temperature, moisture and wind speed often resulting in periodic turbulence. This structure remained well-defined during the plume study, allowing for the detachment of the plume layer from the surface and minimal plume-sea surface exchange. In contrast, shear driven turbulence within the plume layer facilitated lateral mixing with other low-level plumes during its transit. This turbulence was periodic and further contributed to the high spatial variability in trace gas mixing ratios. Further influences of the turbulent mixing were observed in the impact of the plume inland as observed by the Atmospheric Investigation, Regional Modeling, Analysis and Prediction (AIRMAP) air quality network. This impact was seen as extreme elevations of surface ozone and CO levels, equaling the highest observed that summer.

Abstract: Satellite measurements of the spatiotemporal distributions of atmospheric CO2 concentrations are a key component for better understanding global carbon cycle characteristics. Currently, several satellite instruments such as the Greenhouse gases Observing SATellite (GOSAT), SCanning Imaging Absorption Spectrometer for Atmospheric CHartographY (SCIAMACHY), and Orbiting Carbon Observatory-2 can be used to measure CO2 column-averaged dry air mole fractions. However, because of cloud effects, a single satellite can only provide limited CO2 data, resulting in significant uncertainty in the characterization of the spatiotemporal distribution of atmospheric CO2 concentrations. In this study, a new physical data fusion technique is proposed to combine the GOSAT and SCIAMACHY measurements. On the basis of the fused dataset, a gap-filling method developed by modeling the spatial correlation structures of CO2 concentrations is presented with the goal of generating global land CO2 distribution maps with high spatiotemporal resolution. The results show that, compared with the single satellite dataset (i.e., GOSAT or SCIAMACHY), the global spatial coverage of the fused dataset is significantly increased (reaching up to approximately 20%), and the temporal resolution is improved by two or three times. The spatial coverage and monthly variations of the generated global CO2 distributions are also investigated. Comparisons with ground-based Total Carbon Column Observing Network (TCCON) measurements reveal that CO2 distributions based on the gap-filling method show good agreement with TCCON records despite some biases. These results demonstrate that the fused dataset as well as the gap-filling method are rather effective to generate global CO2 distribution with high accuracies and high spatiotemporal resolution.

Abstract: Data from the annual, seasonal, and hourly behavior of the criteria air pollutants CO, NO2, SO2, O3, and PM10 in three Mexican metropolitan areas (the Mexico City Metropolitan Area (MCMA), Guadalajara Metropolitan Area (GMA), and Monterrey Metropolitan Area (MMA)) over the period 2000–2011 were analyzed; and compliance with Mexican air quality standards was evaluated, highlighting causes of specific episodes of high and low concentrations. Data analyzed were collected from automatic air-monitoring networks located in the MCMA (32 stations), GMA (8 stations), and MMA (5 stations). In the MCMA and MMA, correlations between wind direction and concentrations of SO2 suggest that there was a considerable contribution of trans-boundary transport from outside of these areas. Analysis of annual trends revealed large reductions of CO in the MCMA, and SO2 in the three metropolitan areas. However, the annual mean concentration of O3 increased by 47% and 42% in the GMA and MMA, respectively, from 2000 to 2011, but decreased by 13% in the MCMA from 2005 to 2010. The annual mean concentration of PM10 in the MMA was about 58% and 76% higher than that in the MCMA and GMA, respectively, from 2001 to 2010.

Abstract: A severe haze episode that occurred in Wuhan, central China, from 6–14 June 2012 was investigated using ground-based and satellite-derived observations, from which the optical properties and vertical distribution of the aerosols were obtained. The mass concentrations of PM2.5 and black carbon (BC) were 9.9 (332.79 versus 33.66 μg∙m−3) and 3.2 times (9.67 versus 2.99 μg∙m−3) greater, respectively, on haze days than during normal weather. The large aerosol loading contributed to the high values of the scattering (2.32 km−1) and absorption coefficients (0.086 km−1). Particle size became larger, consistent with the reduced scattering Ångström exponent. The high asymmetry parameter (0.65) and single scattering albedo (SSA) (0.97) observed in the haze, which coincided with the relatively low backscatter ratio (0.11) and up-scatter fraction (0.23), were related to the increased particle size, and could have had a heating effect on the atmosphere. Aerosols accumulated primarily below 3 km and according to CALIPSO, were regular in their shapes. At the surface, the aerosol extinction coefficient detected by satellite remained at ~1 km−1, very close to the ground-based observations. Aerosol optical properties measured at this downtown site could help further the understanding of the effects of aerosols on the air quality, city environment, and radiation balance.

Abstract: Samples of PM10 and PM2.5 were collected discontinuously between 2003 and 2010 at fifteen monitoring sites (urban, background, industrial) in the south-eastern part of Italy using a mobile laboratory. In total, 483 PM10 and 154 PM2.5 samples were collected and chemically analyzed for the determination of metal content. Data were used to investigate concentration differences among the typologies of sites, the seasonal patterns, and the influence of advection of Saharan dust (SD). PM10 and PM2.5 average concentrations increase from background to industrial and urban sites but the ratio PM2.5/PM10 is significantly lower (0.61 ± 0.10) in background sites. The average metals concentrations in PM10 and in PM2.5 do not show a clear dependence on site typology apart an increase in crustal elements in background sites and an increase in the enrichment factors of Ni and of Cr in PM10 in industrial sites. Urban sites show a statistically significant increase of PM10 average concentration during the cold seasons (autumn and winter), likely associated with the anthropogenic urban emissions, instead, the background sites show a decrease in concentrations during the cold seasons. This could be due to more frequent cases of SD observed in spring and summer periods that mainly influence background sites. The seasonal difference on the average concentration for industrial sites is not statistically significant. The SD cases influence both PM10 and PM2.5 concentrations but their effect is significantly larger on PM10. Over the studied area, the effect is relatively limited on long-term average PM10 (estimated increase of 3.2%) and PM2.5 (estimated increase of 1.5%) concentrations but it is significant on daily concentrations. It is estimated an increase of 22% of the probability to overcome the air quality standard daily threshold for PM10.

Abstract: This study reports a multi-year (2000–2009) aerosol characterization for metropolitan Tehran and surrounding areas using multiple datasets (Moderate Resolution Imaging Spectroradiometer (MODIS), Multi-angle Imaging Spectroradiometer (MISR), Total Ozone Mapping Spectrometer (TOMS), Goddard Ozone Chemistry Aerosol Radiation and Transport (GOCART), and surface and upper air data from local stations). Monthly trends in aerosol characteristics are examined in the context of the local meteorology, regional and local emission sources, and air mass back-trajectory data. Dust strongly affects the region during the late spring and summer months (May–August) when aerosol optical depth (AOD) is at its peak and precipitation accumulation is at a minimum. In addition, the peak AOD that occurs in July is further enhanced by a substantial number of seasonal wildfires in upwind regions. Conversely, AOD is at a minimum during winter; however, reduced mixing heights and a stagnant lower atmosphere trap local aerosol emissions near the surface and lead to significant reductions in visibility within Tehran. The unique meteorology and topographic setting makes wintertime visibility and surface aerosol concentrations particularly sensitive to local anthropogenic sources and is evident in the noteworthy improvement in visibility observed on weekends. Scavenging of aerosol due to precipitation is evident during the winter when a consistent increase in surface visibility and concurrent decrease in AOD is observed in the days after rain compared with the days immediately before rain.